Utility lines for water, electricity, gas, telephone, and cable television are often run underground for reasons of safety and aesthetics. Sometimes, the underground utilities can be buried in a trench that is subsequently back filled. However, trenching can be time consuming and can cause substantial damage to existing structures or roadways. Consequently, alternative techniques such as horizontal directional drilling (HDD) are becoming increasingly more popular.
A typical horizontal directional drilling machine includes a frame on which is mounted a drive mechanism that can be slidably moved along the longitudinal axis of the frame. The drive mechanism is adapted to rotate a drill string about its longitudinal axis. The drill string comprises a series of drill pipes threaded together. Sliding movement of the drive mechanism along the frame, in concert with the rotation of the drill string, causes the drill string to be longitudinally advanced into or withdrawn from the ground.
In a typical horizontal directional drilling sequence, the horizontal directional drilling machine drills a hole into the ground at an oblique angle with respect to the ground surface. To remove cuttings and dirt during drilling, drilling fluid is pumped by a pump system through the hollow drill string, over a drill head (e.g., a cutting or boring tool) at the end of the drill string, and back up through the hole. After the drill head reaches a desired depth, the drill head is then directed along a substantially horizontal path to create a horizontal hole. Once the desired length of hole has been drilled, the drill head is then directed upwards to break through the ground surface, completing a pilot bore. Alternatively, the drill head may terminate in a trench.
The diameter of the pilot bore so constructed typically must be enlarged. To accomplish this, a reamer (sometimes called a back reamer) is attached to the drill string which is pulled back along the path of the pilot hole, thus reaming out the hole to a larger diameter. The reamer usually includes a reaming or cutting surface on which is mounted cutting teeth or other cutting or grinding elements. It is also common to attach a utility line or other conduit product to the reamer so that the product is pulled through the hole behind the reamer as the reamer enlarges the hole.
A back reamer, then, may perform several functions including: mechanically cutting, grinding and loosening the soil to enlarge the pilot hole diameter, directing drilling fluid to assist in the cutting action, mixing the loosened soil with the drilling fluid such that the resulting slurry is a consistency that will flow out of the bore when displaced by whatever product is to be pulled in, and transferring the longitudinal force required to pull the product through the hole.
The back reamer is normally constructed of heavy duty steel, and comes in many different sizes to create a bore which accommodates the utility product. The back reamer also has many different configurations according to the type of soil being drilled.
Once the pilot hole is completed, a person removes the drilling head and installs the back reamer. This manual operation is dangerous, since the person typically stands in front of or straddles over the top of the reamer in order to install the reamer on the drill string.
Communication errors are known to occur, with a resulting premature actuation of the back reamer while the installer is still preparing the reamer, thus causing serious injury, and even death, to the installer. The heavy weight of the reamer also results in back problems for the installer, both during attachment of the reamer and detachment of the reamer after the utility hole is formed. Furthermore, attachment and detachment of the reamer normally requires the use of large and heavy wrenches, which also may cause injuries if the wrenches are dropped or slipped.
Therefore, a primary objective of the present invention is the provision of an improved back reamer having components which can be quickly and easily assembled and disassembled by one person.
Another objective of the present invention is the provision of an improved back reaming method of horizontal directional drilling using a back reamer having separable components.
Another objective of the present invention is the provision of an improved back reamer having a main shaft, a reamer head, and a pull tab, each of which include faceted faces to prevent rotation relative to one another after the components are assembled.
Another objective of the present invention is the provision of a back reamer having separable components having faceted surfaces to prevent rotation of the components relative to one another.
A further objective of the present invention is an improved back reamer which can be quickly and easily mounted and dismounted from the drill pipe.
A further objective of the present invention is the provision of a method of horizontal directional drilling wherein the back reamer has components which are fixed against rotation relative to one another.
Still another objective of the present invention is an improved method of horizontal directional drilling which minimizes risk of injury to the operator, while effectively and efficiently enlarging the diameter of a pre-drilled pilot hole.
These and other objectives will become apparent from the following description of the invention.